In the code sample below, we will add a custom button and when we click on it, an alert message is displayed.

<?php
require_once 'jq-config.php';
// include the jqGrid Class
require_once "php/jqGrid.php";
// include the driver class
require_once "php/jqGridPdo.php";
// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);
// Tell the db that we use utf-8
$conn->query("SET NAMES utf8");

// Create the jqGrid instance
$grid = new jqGridRender($conn);
// Write the SQL Query
$grid->SelectCommand = 'SELECT OrderID, OrderDate, CustomerID, ShipName, Freight FROM orders';
// Set output format to json
$grid->dataType = 'json';
// Let the grid create the model
$grid->setColModel();
// Set the url from where we obtain the data
$grid->setUrl('grid.php');
// Set some grid options
$grid->setGridOptions(array(
    "rowNum"=>10,
    "rowList"=>array(10,20,30),
    "sortname"=>"OrderID"
));

// Enable navigator
$grid->navigator = true;
// Disable some actions
$grid->setNavOptions('navigator', array("excel"=>false,"add"=>false,"edit"=>false,"del"=>false,"view"=>false));
// add a custom button via the build in callGridMethod
// note the js: before the function
$buttonoptions = array("#pager",
    array("caption"=>"Custom Button", "onClickButton"=>"js: function(){alert('Custom Button clicked')}")
);
$grid->callGridMethod("#grid", "navButtonAdd", $buttonoptions); 

$grid->renderGrid('#grid','#pager',true, null, null, true,true);
$conn = null;
?>